net/mlx5: Disallow RoCE on lag device

In lag mode, setting roce enabled/disable of lag device have no effect.
e.g.: bond device (roce/vf_lag) roce status remain unchanged.
Therefore disable it and add an error message.

Fixes: cc9defcb

 ("net/mlx5: Handle "enable_roce" devlink param")
Signed-off-by: Shay Drory <shayd@nvidia.com>
Reviewed-by: Moshe Shemesh <moshe@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>